The present invention relates to analog optical transmission systems, and more particularly to an apparatus and method for canceling distortion components introduced by a laser transmitter.
Optical transmission systems are currently being implemented for use in various communication applications. For example, telephone systems are now in use that utilize fiber optic technology to transmit voice and data signals over long distances. Similarly, cable television networks are now available wherein fiber optic technology is used for the transmission of both analog and digital signals.
Prior to the implementation of optical transmission networks, cable television programs were carried as radio frequency ("RF") signals over electrical coaxial cables. In fiber optic transmission systems, communication lasers are used for the transmission of the multichannel television signals. The RF signals are used to modulate a light source, and the modulated light is transmitted along the length of an optical fiber.
Optical transmission systems provide substantial benefits, including a virtually unlimited bandwidth and improved system performance. However, harmonic distortion is a major limitation in analog amplitude modulated optical communication transmission systems. Such distortion, and particularly second order distortion, is introduced by the laser which transmits signals over the optical communication system.
It would be advantageous to provide a method and apparatus for canceling second and higher even order distortion in an analog optical transmission system. It would be further advantageous to provide such a method and apparatus that is economical, readily manufacturable, and reliable. The present invention provides a method and apparatus for providing these and other advantages.